Exploring the feasibility of a meta-structure for DSM-V and ICD-11: could it improve utility and validity?

BACKGROUND: The organization of mental disorders into 16 DSM-IV and 10 ICD-10 chapters is complex and based on clinical presentation. We explored the feasibility of a more parsimonious meta-structure based on both risk factors and clinical factors. METHOD: Most DSM-IV disorders were allocated to one of five clusters as a starting premise. Teams of experts then reviewed the literature to determine within-cluster similarities on 11 predetermined validating criteria. Disorders were included and excluded as determined by the available data. These data are intended to inform the grouping of disorders in the DSM-V and ICD-11 processes. RESULTS: The final clusters were neurocognitive (identified principally by neural substrate abnormalities), neurodevelopmental (identified principally by early and continuing cognitive deficits), psychosis (identified principally by clinical features and biomarkers for information processing deficits), emotional (identified principally by the temperamental antecedent of negative emotionality), and externalizing (identified principally by the temperamental antecedent of disinhibition). CONCLUSIONS: Large groups of disorders were found to share risk factors and also clinical picture. There could be advantages for clinical practice, public administration and research from the adoption of such an organizing principle.

DARPP-32: regulator of the efficacy of dopaminergic neurotransmission.

Dopaminergic neurons exert a major modulatory effect on the forebrain. Dopamine and adenosine 3',5'-monophosphate-regulated phosphoprotein (32 kilodaltons) (DARPP-32), which is enriched in all neurons that receive a dopaminergic input, is converted in response to dopamine into a potent protein phosphatase inhibitor. Mice generated to contain a targeted disruption of the DARPP-32 gene showed profound deficits in their molecular, electrophysiological, and behavioral responses to dopamine, drugs of abuse, and antipsychotic medication. The results show that DARPP-32 plays a central role in regulating the efficacy of dopaminergic neurotransmission.

Neuronal adaptation to amphetamine and dopamine: molecular mechanisms of prodynorphin gene regulation in rat striatum.

Induction of prodynorphin gene expression by psychostimulant drugs may represent a compensatory adaptation to excessive dopamine stimulation and may contribute to the aversive aspects of withdrawal. We therefore investigated the molecular mechanisms by which dopamine psychostimulant drugs induce prodynorphin gene expression in vivo and in rat primary striatal cultures. We demonstrate that three recently described cAMP response elements (CREs), rather than a previously reported noncanonical AP-1 site, are critical for dopamine induction of the prodynorphin gene in striatal neurons. CRE-binding protein (CREB) binds to these CREs in striatal cell extracts and is phosphorylated on Ser-133 after dopamine stimulation in a D1 dopamine receptor-dependent manner. Surprisingly, following chronic administration of amphetamine, levels of phosphorylated CREB are increased above basal in rat striatum in vivo, whereas c-fos mRNA is suppressed below basal levels. D1 receptor-mediated CREB phosphorylation appears to mediate adaptations to psychostimulant drugs in the striatum.

Dopamine and glutamate induce distinct striatal splice forms of Ania-6, an RNA polymerase II-associated cyclin.

Control of neuronal gene expression by drugs or neurotransmitters is a critical step in long-term neural plasticity. Here, we show that a gene induced in the striatum by cocaine or direct dopamine stimulation, ania-6, is a member of a novel family of cyclins with homology to cyclins K/T/H/C. Further, different types of neurotransmitter stimulation cause selective induction of distinct ania-6 isoforms, through alternative splicing. The longer Ania-6 protein colocalizes with nuclear speckles and is associated with key elements of the RNA elongation/processing complex, including the hyperphosphorylated form of RNA polymerase II, the splicing factor SC-35, and the p110 PITSLRE cyclin-dependent kinase. Distinct types of neuronal stimulation may therefore differentially modulate nuclear RNA processing, through altered transcription and splicing of ania-6.

Response and habituation of the human amygdala during visual processing of facial expression.

We measured amygdala activity in human volunteers during rapid visual presentations of fearful, happy, and neutral faces using functional magnetic resonance imaging (fMRI). The first experiment involved a fixed order of conditions both within and across runs, while the second one used a fully counterbalanced order in addition to a low level baseline of simple visual stimuli. In both experiments, the amygdala was preferentially activated in response to fearful versus neutral faces. In the counterbalanced experiment, the amygdala also responded preferentially to happy versus neutral faces, suggesting a possible generalized response to emotionally valenced stimuli. Rapid habituation effects were prominent in both experiments. Thus, the human amygdala responds preferentially to emotionally valenced faces and rapidly habituates to them.

Acute effects of cocaine on human brain activity and emotion.

We investigated brain circuitry mediating cocaine-induced euphoria and craving using functional MRI (fMRI). During double-blind cocaine (0.6 mg/kg) and saline infusions in cocaine-dependent subjects, the entire brain was imaged for 5 min before and 13 min after infusion while subjects rated scales for rush, high, low, and craving. Cocaine induced focal signal increases in nucleus accumbens/subcallosal cortex (NAc/SCC), caudate, putamen, basal forebrain, thalamus, insula, hippocampus, parahippocampal gyrus, cingulate, lateral prefrontal and temporal cortices, parietal cortex, striate/extrastriate cortices, ventral tegmentum, and pons and produced signal decreases in amygdala, temporal pole, and medial frontal cortex. Saline produced few positive or negative activations, which were localized to lateral prefrontal cortex and temporo-occipital cortex. Subjects who underwent repeat studies showed good replication of the regional fMRI activation pattern following cocaine and saline infusions, with activations on saline retest that might reflect expectancy. Brain regions that exhibited early and short duration signal maxima showed a higher correlation with rush ratings. These included the ventral tegmentum, pons, basal forebrain, caudate, cingulate, and most regions of lateral prefrontal cortex. In contrast, regions that demonstrated early but sustained signal maxima were more correlated with craving than with rush ratings; such regions included the NAc/SCC, right parahippocampal gyrus, and some regions of lateral prefrontal cortex. Sustained negative signal change was noted in the amygdala, which correlated with craving ratings. Our data demonstrate the ability of fMRI to map dynamic patterns of brain activation following cocaine infusion in cocaine-dependent subjects and provide evidence of dynamically changing brain networks associated with cocaine-induced euphoria and cocaine-induced craving.

Inhibiting activator protein-1 activity alters cocaine-induced gene expression and potentiates sensitization.

We have expressed A-FOS, an inhibitor of activator protein-1 (AP-1) DNA binding, in adult mouse striatal neurons. We observed normal behavior including locomotion and exploratory activities. Following a single injection of cocaine, locomotion increased similarly in both the A-FOS expressing and littermate controls. However, following repeated injections of cocaine, the A-FOS expressing mice showed increased locomotion relative to littermate controls, an increase that persisted following a week of withdrawal and subsequent cocaine administration. These results indicate that AP-1 suppresses this behavioral response to cocaine. We analyzed mRNA from the striatum before and 4 and 24 h after a single cocaine injection in both A-FOS and control striata using Affymetrix microarrays (430 2.0 Array) to identify genes mis-regulated by A-FOS that may mediate the increased locomotor sensitization to cocaine. A-FOS expression did not change gene expression in the basal state or 4 h following cocaine treatment relative to controls. However, 24 h after an acute cocaine treatment, 84 genes were identified that were differentially expressed between the A-FOS and control mice. Fifty-six genes are down-regulated while 28 genes are up-regulated including previously identified candidates for addiction including brain-derived neurotrophic factor and period homolog 1. Using a random sample of identified genes, quantitative PCR was used to verify the microarray studies. The chromosomal location of these 84 genes was compared with human genome scans of addiction to identify potential genes in humans that are involved in addiction.

Selective gene expression increases behavioral sensitivity to cocaine.

Addictive drugs induce a truncated form of fosB in the striatum. A new study shows that mice engineered to mimic this expression pattern are abnormally sensitive to cocaine.

An AP-2 element acts synergistically with the cyclic AMP- and phorbol ester-inducible enhancer of the human proenkephalin gene.

An enhancer with two DNA elements, one containing the sequence CGTCA, is required for cyclic AMP- and phorbol ester-inducible transcription of the human proenkephalin gene. We report that an AP-2 element located adjacent to the enhancer acts synergistically with it to confer maximal response to cyclic AMP and phorbol esters.

A common trans-acting factor is involved in transcriptional regulation of neurotransmitter genes by cyclic AMP.

Activation of neurotransmitter receptors can regulate transcription in postsynaptic cells through the actions of second messengers. Trans-synaptic regulation of transcription appears to be an important mechanism controlling the synthesis of molecules involved in neuronal signaling, especially neuropeptides. Proenkephalin, vasoactive intestinal polypeptide, and somatostatin have been shown to be transcriptionally regulated by the second messenger, cyclic AMP (cAMP), as has the catecholamine synthesizing enzyme tryosine hydroxylase. cAMP-inducible elements have been mapped within these genes, and trans-acting factors which bind to several such elements have been identified. With the discovery that individual neurons generally contain multiple transmitters within their synaptic terminals, it has become important to understand in detail the mechanisms by which the synthesis of transmitters can be coregulated. Here we compare the structure and function of the proenkephalin cAMP-inducible enhancer with the mapped cAMP-inducible elements of the vasoactive intestinal polypeptide, somatostatin, and tyrosine hydroxylase genes and a putative cAMP-inducible element in the proto-oncogene c-fos. We have previously shown that the proenkephalin enhancer is composed of two different elements, ENKCRE-1 and ENKCRE-2. We show here that one of these, ENKCRE-2, is structurally similar to elements found within the vasoactive intestinal polypeptide, somatostatin, and tyrosine hydroxylase genes and binds a trans-acting factor that is competed for both in cotransfection experiments (in vivo) and in DNase I footprint assays (in vitro) by these other elements. The c-fos element has similar structural requirements to confer transcriptional induction by cAMP but competes less strongly. Protein purified by affinity chromatography with the ENKCRE-2 sequence binds to each of these elements. A second element within the proenkephalin cAMP-inducible enhancer, ENKCRE-1, binds a factor that is not competed for by these other genes and is therefore distinct. This analysis suggests a potential mechanism of transcriptional coregulation of the neuronally expressed genes investigated in this study and also demonstrates that multiple factors are involved in transcriptional activation by cAMP.

The millennium of mind, brain, and behavior.

Psychiatry enters the new millennium poised to answer many of its central questions. Given the complexity of the human brain and its interactions with our world, these questions are among the most difficult ever addressed by human science. How is the human brain built? How does it change over the life span? What are the precise genetic and environmental risk factors for mental illnesses? What are the pathophysiologic processes that produce the symptoms and disabilities? How do our treatments, including psychotherapy, work? What objective markers can we discover to monitor the progression of the pathogenic processes and the effects of treatment? How will we discover preventive measures and cures that will be effective in diverse populations and settings? Parallel to the pursuit of its public health agenda, psychiatry will grow closer to neuroscience, behavioral science, and neurology. In so doing, those who practice these disciplines will be better positioned to ask meaningful questions about the relationship among mind, brain, and behavior, and to finally overcome the pervasive Cartesianism that continues to incubate stigma and ignorance about mental illness.

Molecular mechanisms of stress-induced proenkephalin gene regulation: CREB interacts with the proenkephalin gene in the mouse hypothalamus and is phosphorylated in response to hyperosmolar stress.

We have established a transgenic model to facilitate the study of stress-induced gene regulation in the hypothalamus. This model, which uses a human proenkephalin-beta-galactosidase fusion gene, readily permits anatomic and cellular colocalization of stress-regulated immediate early gene products (e.g. Fos) and other transcription factors [e.g. cAMP response element-binding protein (CREB)] with the product of a potential target gene. Moreover, Fos provides a marker of cellular activation that is independent of the transgene. Hypertonic saline stress induced Fos in almost all cells in the PVN that exhibited basal expression of the proenkephalin transgene; however, all cells in which the transgene was activated by stress also expressed Fos. CREB was found in essentially all neurons. Gel shift analysis with and without antisera to Fos and CREB showed that AP-1 binding activity, containing Fos protein, was induced by hyperosmotic stress. However, Fos was not detected binding to the proenkephalin second messenger-inducible enhancer even in hypothalamic cell extracts from stressed animals. In contrast, CREB formed specific complexes with both the proenkephalin enhancer and a cAMP- and calcium-regulated element (CaRE) within the c-fos gene. Moreover, we found that hypertonic saline induced CREB phosphorylation in cells that express the transgene within the paraventricular nucleus and supraoptic nucleus. These results suggest a model in which proenkephalin gene expression in the paraventricular nucleus is regulated by CREB in response to hypertonic stress.

STAT proteins participate in the regulation of the vasoactive intestinal peptide gene by the ciliary neurotrophic factor family of cytokines.

Ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) are members of a family of neuropoietic cytokines that have a broad range of actions on many different neuronal populations. In cultured sympathetic neurons, CNTF and LIF induce transcription of the VIP and other neuropeptide genes as part of a program of differentiation. To gain insight into the nuclear events involved in cytokine-mediated activation of the neuropeptide genes involved in neuronal differentiation, we have investigated the mechanisms of transcriptional activation of the vasoactive intestinal peptide (VIP) gene by the CNTF family of cytokines. In the neuroblastoma cell line NBFL, CNTF, LIF, and a related cytokine, oncostatin-M, activate VIP gene transcription through a 180-base pair cytokine response element (CyRE). Deletion analysis of the VIP CyRE showed that multiple regions within the 180 base-pairs are important for cytokine-mediated transcriptional activation of the VIP gene. To one of these regions within the CyRE, cytokine treatment induces binding of a protein complex composed of members of the signal transducers and activators of transcription (STAT) transcription factor family. Mutation of this STAT-binding site attenuates cytokine-mediated transcriptional activation. LIF treatment of primary sympathetic neurons also induced binding of a STAT-containing protein complex to the VIP CyRE. Thus, activation of STAT transcription factors contributes to the induction of the VIp gene by the CNTF family of cytokines and may be involved in cytokine-mediated differentiation of sympathetic neurons.

Expression and regulation of a proenkephalin beta-galactosidase fusion gene in the reproductive system of transgenic mice.

A fusion gene containing 3 kilobases of human proenkephalin 5'-flanking sequences and 1 kilobase of human proenkephalin 3'-flanking sequence and the easily visualized histochemical marker, Escherichia coli beta-galactosidase, was used to study the function of cis-regulatory elements within the human proenkephalin gene in transgenic mice. Here data are presented on expression and regulation of this fusion gene in the reproductive system of three independent lines of transgenic mice. Within the male reproductive system, the fusion gene is expressed in the proximal epididymis and in developing germinal cells but not in mature or elongating spermatids. In the female reproductive system, the transgene was expressed at low basal levels, but expression was dramatically stimulated in the ovary and oviduct by hormonal stimulation and pregnancy; additionally, expression was induced at the uteroplacental junction in pregnant mice. Taken together these observations suggest that critical sequences for expression and regulation of the proenkephalin gene within the reproductive system are contained within sequences of the construct.

Stress-induced regulation of a human proenkephalin-beta-galactosidase fusion gene in the hypothalamus of transgenic mice.

Transgenic mice expressing an Escherichia coli beta-galactosidase reporter gene under the control of 3 kilobases of human proenkephalin gene 5'-flanking sequence and 1.2 kilobases of 3'-flanking sequence exhibited an anatomically correct pattern of basal and stress-regulated transgene expression within the hypothalamus. Acute osmotic stress and hypovolemia induced transgene expression in neurons within both the paraventricular and supraoptic nuclei. Chronic osmotic stress resulted in dramatic induction of transgene expression in both nuclei. These results demonstrate that the information required for correct hypothalamic expression and stress regulation of the proenkephalin gene is contained within our fusion construct.

Goals for research on bipolar disorder: the view from NIMH.

We have much yet to accomplish in research on bipolar disorder. We must find vulnerability genes. We must identify the circuits that regulate mood, emotion, energy, and other relevant functions that are affected in bipolar disorder, and we must determine what goes wrong in those circuits during mania, depression, and other aspects of this illness. We will need to translate findings in basic neuroscience, genetics, and basic behavioral science into diverse clinical applications: novel treatments, diagnostic tools, epidemiologic approaches that could lead to preventive interventions, and surrogate markers for clinical trials. We must develop improved psychosocial interventions and test both pharmacologic and psychosocial treatments in trials that, simultaneously, improve the quality of care available and convince insurers and employers that these treatments are of substantial benefit and cost effective. The agenda is ambitious, but entirely feasible, given the scientific tools and technologies that are currently available or on the horizon. The National Institute of Mental Health is newly recommitted to harnessing these tools and technologies for the benefit of people with bipolar disorder.

Cocaine decreases cortical cerebral blood flow but does not obscure regional activation in functional magnetic resonance imaging in human subjects.

The authors used functional magnetic resonance imaging (fMRI) to determine whether acute intravenous (i.v.) cocaine use would change global cerebral blood flow (CBF) or visual stimulation-induced functional activation. They used flow-sensitive alternating inversion recovery (FAIR) scan sequences to measure CBF and blood oxygen level-dependent (BOLD) sensitive T2* scan sequences during visual stimulation to measure neuronal activation before and after cocaine and saline infusions. Cocaine (0.6 mg/kg i.v. over 30 seconds) increased heart rate and mean blood pressure and decreased end tidal carbon dioxide (CO2). All measures returned to baseline by 2 hours, the interinfusion interval, and were unchanged by saline. Flow-sensitive alternating inversion recovery imaging demonstrated that cortical gray matter CBF was unchanged after saline infusion (-2.4 +/- 6.5%) but decreased (-14.1 +/- 8.5%) after cocaine infusion (n = 8, P < 0.01). No decreases were detected in white matter, nor were changes found comparing BOLD signal intensity in cortical gray matter immediately before cocaine infusion with that measured 10 minutes after infusion. Visual stimulation resulted in comparable BOLD signal increases in visual cortex in all conditions (before and after cocaine and saline infusion). Despite a small (14%) but significant decrease in global cortical gray matter CBF after acute cocaine infusion, specific regional increases in BOLD imaging, mediated by neurons, can be measured reliably.

Initiation and adaptation: a paradigm for understanding psychotropic drug action.

OBJECTIVE: This article describes a paradigm--initiation and adaptation--within which to conceptualize the drug-induced neural plasticity that underlies the long-term actions of psychotropic drugs in the brain. METHOD: Recent advances in neurobiology are reviewed. RESULTS: Recent developments in cellular and molecular neurobiology provide new conceptual and experimental tools for understanding the mechanisms by which psychotropic drugs produce long-lived alterations in brain function. Because of the availability of more robust animal models, the mechanisms by which drugs of abuse produce dependence are better understood than the mechanisms by which antidepressants, antipsychotics, and lithium produce their therapeutic effects. Nonetheless, the fundamental types of mechanisms appear to be similar: chronic drug administration drives the production of adaptations in postreceptor signaling pathways, including regulation of neural gene expression. Whether the results are deleterious or therapeutic depends on the precise neural systems targeted by a particular drug. CONCLUSIONS: Biological investigation in psychiatry has often focused too narrowly on synaptic pharmacology, especially on neurotransmitter turnover and neurotransmitter receptors. This review focuses on molecular and cellular changes in neural function that are produced as adaptations to chronic administration of addictive drugs such as psychostimulants and therapeutic drugs such as antidepressants. To understand normal brain function, psychopathology, and the actions of psychiatric treatments, and to exploit the eventual findings of psychiatric genetics, psychiatric research must now extend its efforts beyond the synapse, to an understanding of cellular and molecular neurobiology (in particular, postreceptor signal transduction) as well as to a better understanding of the architecture and function of neural systems. A paradigm is presented to help understand the long-term effects of psychotropic drugs, including the latency in onset of their therapeutic actions.

Substance P phenotype defines specificity of c-fos induction by cocaine in developing rat striatum.

Activation of c-fos, a member of the class of immediate early genes that act as transcription factors, may be one of the initial molecular mechanisms underlying plastic changes in gene expression in response to drugs of abuse. By combining c-fos (radioactive) in situ hybridization histochemistry with nonradioactive in situ hybridization histochemistry for mRNAs encoding other striatal markers [preprotachykinin (substance P), proenkephalin, and D1 and D2 receptors], we have identified the cellular phenotype of striatal neurons activated by acute administration of cocaine to P8, P15, P28, and adult rats. At each age examined, substance P+, enkephalin- striatal neurons were the predominant class of cells in which cocaine induced c-fos gene expression. In addition, the topography of cellular activation at each age examined was distinct and reflected the topography of distribution of cells expressing high levels of substance P mRNA. We conclude that there is a marked specificity of cellular activation in striatum following acute cocaine administration restricted predominantly to subsets of substance P-expressing cells, with age-specific patterns in their topographic distribution.

Postnatal age defines specificity of immediate early gene induction by cocaine in developing rat brain.

Clinical and animal data suggest that exposure of developing brain to cocaine has adverse consequences. One candidate mechanism for such effects is drug regulation of gene expression. In adult rats, cocaine induces expression of nuclear immediate early genes with specific spatial and temporal patterns. The products of such genes (e.g., c-Fos, c-Jun, and Zif/268) subserve the coupling of cell surface receptor stimulation to transcriptional regulation. Thus, activation of immediate early gene expression in developing brain by cocaine could alter programs of neural gene expression and, thereby, neuronal phenotype and function. We report that, during rat brain development, cocaine produced brain region-specific and developmental age-specific induction of c-fos, c-jun, and zif/268 mRNAs. At each age studied (P8, P15, P28, and adults), we found that acute cocaine administration resulted in a unique cell-specific pattern of c-fos mRNA induction and c-Fos protein expression in striatum. We also observed cocaine-induced activation of AP-1 DNA binding activity in striatal extracts prepared at these different ages, suggesting that the observed induction of c-fos and c-jun may have biological consequences for the developing brain. These findings suggest a mechanism by which cocaine could alter patterns of gene expression during critical developmental periods with differential regional, temporal, and cellular vulnerabilities and, therefore, consequences for developing brain.